The present invention relates to a device for controlling a power supplying device which supplies power to a plurality of systems to be supplied with different voltages.
A power supplying device for supplying current from a 100 volts A.C. power supply to a plurality of DC systems that utilize different voltages. is known When the power supply is turned off and 100 volts a.c. is cut off, for instance, the voltage from the power supply will be attenuated transiently until the voltage settles at 0 volt.
Consequently, the voltages in the two DC systems gradually drop down to 0 volt ultimately. However, as the voltage drop slopes are similar to each other, the low-voltage drops to 0 volt before the high-voltage drops to 0 volt.
When the high-voltage is applied to a drive system with the low-voltage applied to a control system, hunting arises in the course of the high-voltage drop. If the power is supplied to the drive system which is not under the control of the control system as the low-voltage has already dropped to 0 volt, malfunctions such as motor vibration may occur.